DESCRIPTION (Applicant?s Abstract): The TNFalpha receptor CD120a (p55) plays a critical role in the development of acute and chronic inflammatory diseases of the lung by initiating functions including pro-inflammatory cytokine production, and cell survival and death. Recent work from this laboratory suggests that CD12Oa is localized to plasma membrane rafts in quiescent cells but redistributes primarily to the endoplasmic reticulum following ligand-induced receptor phosphorylation. Therefore we hypothesize that subcellular localization of CD12Oa determines the outcome of TNFalpha stimulation. This hypothesis will be addressed by three specific aims: (i) To determine the mechanisms of CD120a localization to receptor rafts; this will be accomplished by site-directed or ala-scanning mutagenesis. (ii) To determine the mechanism of CD12Oa redistribution following TNFalpha stimulation. Herein, our primary focus will be to address the association of CD120a with the actin-based cytoskeleton through co-precipitation and microscopic analyses. (iii) To determine the requirements for receptor rafts during TNFalpha-induced signaling. Activation of signaling intermediates, the transcription factor NF-kB, and apoptotic processes will be assayed. The outcome of this work will contribute to our understanding of how signaling through CD12Oa is regulated in inflammatory processes in the lung.